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<title>&lt;stddef.h&gt;</title>
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The Single UNIX &reg; Specification, Version 2<br>
Copyright &copy; 1997 The Open Group

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<h4><a name = "tag_000_008_856">&nbsp;</a>NAME</h4><blockquote>
stddef.h - standard type definitions
</blockquote><h4><a name = "tag_000_008_857">&nbsp;</a>SYNOPSIS</h4><blockquote>
<pre><code>

#include &lt;stddef.h&gt;
</code>
</pre>
</blockquote><h4><a name = "tag_000_008_858">&nbsp;</a>DESCRIPTION</h4><blockquote>
The
<i>&lt;stddef.h&gt;</i>
header defines the following:
<dl compact>

<dt>NULL<dd>
Null pointer constant.

<dt>offsetof(<i>type</i>, <i>member-designator</i>)<dd><br>
Integral constant expression of type <b>size_t</b>, the
value of which is the offset in bytes to the structure member
(<i>member-designator</i>),
from the beginning of its structure (<i>type</i>).

</dl>
<p>
The
<i>&lt;stddef.h&gt;</i>
header defines through <b>typedef</b>:
<dl compact>

<dt><b>ptrdiff_t</b><dd><index term="data type, ptrdiff_t"></index>
Signed integral type of the result of subtracting two
pointers.

<dt><b>wchar_t</b><dd><index term="data type, wchar_t"></index>
Integral type whose range of values can represent distinct wide-character
codes for all members of the largest character set specified
among the locales supported by the compilation environment:
the null character has the code value 0 and each member of
the Portable Character Set has a code value
equal to its value when used as the lone character in an integer
character constant.

<dt><b>size_t</b><dd><index term="data type, size_t"></index>
Unsigned integral type of the result of the
<i>sizeof</i>
operator.

</dl>
</blockquote><h4><a name = "tag_000_008_859">&nbsp;</a>APPLICATION USAGE</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_860">&nbsp;</a>FUTURE DIRECTIONS</h4><blockquote>
None.
</blockquote><h4><a name = "tag_000_008_861">&nbsp;</a>SEE ALSO</h4><blockquote>
<i><a href="wchar.h.html">&lt;wchar.h&gt;</a></i>,
<i><a href="systypes.h.html">&lt;sys/types.h&gt;</a></i>.
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UNIX &reg; is a registered Trademark of The Open Group.<br>
Copyright &copy; 1997 The Open Group
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